a) Field of the Invention
The invention is directed to a correction lens system for a particle beam projection device. In particular, the invention is directed to a correction lens system for a particle beam projection device having at least a first magnetic lens and a second magnetic lens.
b) Description of the Related Art
European Patent EP 0 870 316 B1 discloses a multipart magnetic lens with concentric bore holes, conical pole pieces, and a deflecting unit. The lens is axially symmetric, and the conical geometry of the bottom part of the lens allows the magnetic lens field to be moved very close to the substrate. However, the lens does not provide the possibility of separate adjustment of the parameters for focusing, scale change and beam rotation. Usually, slow pole piece lenses are used for rotating the beam. Further, the method for minimizing the eddy currents caused by the focusing lenses in the pole pieces of the pole piece lenses by compensation of the external field was not known heretofore.